In general, amplifiers are used to increase the power of signals. For example, amplifiers can be used to convert low-power radio frequency (RF) signals into larger RF signals for driving the antenna of a transmitter. In such cases, amplifiers may be implemented as part of an overall power amplifier used by an RF transmission system.
Power amplifiers tend to consume a significant portion of the total power consumed by a transmission system. Therefore, the power amplifier's efficiency (i.e., the output power of the amplifier divided by the total DC power supplied to the amplifier) is an amplifier quality that designers consistently strive to increase.
However, amplifier bandwidth and linearity are also important parameters to consider, and many amplifier designs with high theoretical power efficiencies may have characteristically lower fractional bandwidths and reduced linearity. Therefore, there remains a need for amplifiers that provide both relatively high efficiency, relatively high fractional bandwidth, and high linearity.